Separation of bark components



April 1963 A. H. VROOM ET AL 3,086,717

SEPARATION OF BARK COMPONENTS Filed July 22. 1957 5 Sheets-Sheet 1 WETBARK WET DISINTEGRATION NON-FIBROUS FRACTION WATER HYDRAULICCENTRIFUGING FIBROUS FRACTION d WET BARKQ WET DISINTEGRATION NON-FIBROUSFRACTION HYDRAULIC CENTRIFUGING COARSER FIBROUS FRACTION FRACTIONSCREENING F/G.2.

LESS COARSE NON-FIBROUS' FRACTION FRACTION HYDRAULIC CE'NTRIFUGINGINVENTORS ALAN H.VRO0M FIBROUS FRACTION JOHN D. BOADWAY a BY W ATiRNEYs.

April 1963 A. H. VROOM ET AL 3,086,717

SEPARATION OF BARK COMPONENTS Filed July 22. 1957 3 Sheets-Sheet 2 WETBARK WET DISINTEGRATION NON-FIBROUS FRACTION HYDRAULIC CENTRIFUGINGFIBROUS HYDRAULIC FRACTION FLUID SCREENING THICKENING FIBROUS COLLOIDALCOLLOIDAL FRACTION GEL-LIKE GEL-LIKE FRACTION COMPOUND INVENTORS ALANH.VROOM JOHN D. BOADWAY April 1963 A. H. VROOM ET AL 3,086,717

SEPARATION OF BARK COMPONENTS Filed July 22. 1957 3 Sheets-Sheet 3 DRYBARK COARSE DRY D ISINTEGRATION HIGH PROPORTION FIBROUS MATERIAL coARsEDRY SCREENING WATER HIGH PROPORTION wET NON-FIBROUS DISINTEGRATIONMATERIAL WATER WATER WET HYDRAULIC DISINTEGRATION CENTR'FUG'NG WATERHYDRAULIC NON-FIBROUS CENTRIFUGING FRACTIN NON-FIBROUS FIBROUS FRACTIONFRACTION l;|BROU|S RAcT ON INVENTORS ALAN H. vRoo JOHN D- BOADWAY.

ATTORNEY United States Patent 3,085,717 SEPARATEON 9F BARK COMP9NENTAlan H. Vroorn and .Iohn D. Roadway, both of Grand- Mere, Quebec,Canada, assiguors to (Ionsoiidated Paper Corporation Limited, GrandMere,Quebec, Canada Filed July 22, 15 57, Ser. No. 673,131 Claims. (Cl.24124) Our invention relates to the utilization of bark and moreparticularly to a physical separation of the fibrous and non-fibrouscomponents of bark into more useful products for individual use inmanufacturing processes.

It is well known that many types of bark contain a high percentage ofuseful fibrous material. Attempts have been made to reclaim this fiberby cooking the bark either separately or with the original wood beingpresent. These methods have, by and large, been unsuccessful for severalreasons, for example the bark itself consumed abnormal amounts ofexpensive cooking chemicals, a good part of the fibrous fraction of thebark was destroyed during the cooking process, or the properties of thefinal fibrous material Were often very unsatisfactory, as, for example,when use is to be made of the fibrous property of the bark in themanufacture of fiber board the non-fibrous component interferesseriously with the drainage properties of the bark.

Thus any lack of a successful utilization of bark generally results in aproblem of disposal. Many pulp and paper mills attempt to solve thisproblem by discharging the bark into nearby rivers; this in turngenerally results in a pollution problem.

The present process avoids the disadvantages of these chemical methodsof fiber reclamation by employing a physical method to separate thecomponents of the bark. In doing so, the components are separated into aform which is very similar, chemically and physically, to that in whichthey existed in the original whole bark. Having isolated the componentsof the bark, further modification of the components can be made in amore satisfactory and controllable manner.

In the accompanying drawings which illustrate various embodiments of theinvention:

FIG. 1 is a flow diagram of the process using the basic steps of wetdisintegration and hydraulic centrifuging;

FIG. 2 is a flow diagram of an alternate embodiment showing additionalsteps carried out with respect to one of the two final products shown inFIG. 1;

FIG. 3 is a flow diagram of alternate embodiment showing additionalsteps carried out with respect to the fibrous fraction product of FIG.1; and

FIG. 4 is a flow diagram of a further embodiment showing addedpreliminary steps.

The invention, in its broadest aspect as shown in FIG. 1, is a method ofseparating bark into fibrous and nonfibrous components comprising a wetdisintegration of the bark to substantially loosen the non-fibrouscomponent from the fibrous component and a hydraulic centrifuging tosubstantially separate the fibrous component from the non-fibrouscomponent.

In a preferred embodiment of the invention the bark, after wetdisintegration, is suspended in water at a consistency below 1.5representing the proportion by weight of the bark in the hydraulicfluid, and then the bark is subjected to a hydraulic centrifugalseparation of the fibrous and non-fibrous components by pumping thesuspended disintegrated bark through a centrifugal separator of thevortex pressure drop type.

The invention will now be described with reference to an example of themethod as carried out on a commercial scale.

Approximately twenty tons of wet bark comprising roughly 50% balsam and50% spruce, was used in a 3,fi%,7i7 Patented Apr. 23, 1983 particularoperation. The bark was fed to a swinghammer type of shredder set togive a coarse shredded product. This shredded bark was then furtherdisintegrated by passing it through a disk-refiner, of a type used inrefining of papermaking pulps, the plates of the refiner being set togive a medium to light brushing action. The disintegrated bark was thendiluted to a consistency of about 0.5 and then pumped to a centrifugalseparator of the vortex pressure drop type (such as described in theFreeman and Broadway United States patent application No. 493,352, filedMarch 10, 1955, now US. Patent 2,927,693, granted March 8, 1960,entitled Cleaning of Paper Pulp Suspensions an dthe Like). The top oraccepts flow was found to contain a very high proportion of fibrous (orpulp) material while the bottom or rejects flow was found to contain avery high proportion of non-fibrous (or cork-like) material. The fibrousmaterial was thickened on a conventional pulp decker and the non-fibrousmaterial on an inclined wire arrangement.

The resultant fibrous material product has found satisfactory use as apart furnish in the manufacture of specialty paper boards. Thenon-fibrous or cork-like material may be used as a chemical carrier,soil conditioner, filler and insulating material. A dissolved orcolloidal gel-like material (a pectin-like material such aspolygalacturonic acid) found in the efiiuent from the thickeningoperation of the fibrous material may also be used, for example as abinding agent or as a source of chemical raw material. Applicant hasfound that this latter colloidal material will tend to separate from themain body of the efiluent simply upon standing and can be recovered byskimming from the bulk of the hydraulic fluid. Some of the colloidal ordissolved material may also be recovered by a pressing operation afteran initial disintegration of the bark.

The processes of disintegrating and centrifuging, de scribed above, maybe interchanged in part or extended. For example, a centrifugalseparation may be made after a coarse wet disintegration. The materialfrom the centrifugal separator in one or both flows may then be furtherdisintegrated, followed by a further centrifugal separation. Forexample, the non-fibrous fraction of FIG. 1 can be further processed inthe same manner as disclosed in the steps of FIG. 1. Alternatively, thematerial of one of the centrifugal flows may be rediluted, if necessary,and pumped through a second centrifugal separator to separate thecomponents to a still finer degree.

Sometimes the nature of the bark or the presence of some non-barkmaterial with the bark makes it desirable to introduce a screeningoperation, for example the known method of rotary screening as practisedin the pulp and paper industry, into the sequence of the above steps. Asan example shown in FIG. 2, when much wood is present with the bark, wehave found it advisable to do the following: disintegrate the mixture ofbark and wood, centrifuge the diluted mixture so that a relatively pureor non-fibrous (or corklike) bulk component is rejected, screen theaccepted flow (that is, the top fraction) in a rotary screen so that thecoarse woody fraction is rejected, return this rejected fraction to theinitial disintegrating operation, and centrifuge the accepted fractionto remove most of the remaining non-fibrous (or cork-like) material.This yields a fairly pure fibrous product. Alternatively, as shown inFIG. 3 the fibrous fraction is screened after the basic steps toseparate out the colloidal gel-like material, as described earlier; andthe step of thickening, or settling and skimming follows. FIG. 4 showsanother example of an adaption of the disintegration steps together withthe introduction of known screening operations into the sequence of theabove mentioned steps. Where the bark is sufficiently dry for asatisfactory dry disintegration, this may be done very coarsely in someshredder type equipment, and the material dry screened on a very coarsescreen to yield essentially two fractions, a plus or rejected fractionconsisting of a high proportion of fibrous material and a minus oraccepted fraction consisting of a high proportion of non-fibrousmaterial; either or both of these fractions may then be treated asindicated above in FIG. 1, that is, a wet disintegration followed by acentrifugal separation to further separate the fibrous from thenon-fibrous fraction.

Thus, depending on the nature of the bark, the type of material desired,and the type of equipment available, the two main operations ofdisintegration and centrifugal separation may be adjusted and arrangedto give the desired resultant products.

The choice of disintegrating equipment will depend on several factors,for example the actual types of equipment available and the type ofseparation and nature of the final product desired. As described above,by way of example, a combination of a swing-hammer type with a disk-typerefiner for final disintegration was found successful. It is possible,however, that one disintegrator could do both operations. Thedisintegration methods discussed here also include such methods as areexemplified by the explosion-type processes used in the mmufacture ofMasonite fiber. (Masonite, a trademark, refers to a grainlessmanufactured board made entirely from wood fibers wherein wood chips areexploded under high steam pressure.)

While there are several types of hydraulic centrifuges which could carryout the centrifugal operation to some degree of completion, ourpreference is for those of the vortex pressure drop type of centrifugewhere the forces of liquid shear play a part in selecting and separatingparticles of different shape, in spite of the fact that the particlesmay have similar specific gravities.

What we claim as our invention is:

1. A method of separating bark, of the type having a fibrous andgel-like component into its physical components which comprises a wetdisintegration of the bark to substantially loosen the solid non-fibrouscomponents fiom the fibrous and colloidal gel-like component, ahydraulic centrifuging in a vortex pressure drop type centrifugalseparator to substantially separate the said nonfibrous component fromthe said fibrous and gel-like components, screening the fibrouscomponent to separate the said fibrous component as an oversize productfrom the fluid and said colloid-a1 gel-like component as a throughsproduct, and thickening to separate the colloidal gel-like componentfrom the bulk of the hydraulic fluid.

2. A method of separating bark, of the type having a fibrous component,into fibrous and non-fibrous components which comprises a coarse drydisintegration of the bark, a coarse dry screening to yield twofractions, one fraction containing a higher percentage of the fibrouscomponent and the other fraction containing a higher percentage of thenon-fibrous component, adding water to at least one of said fractions toincrease its water content, a wet disintegration of this dilutedfraction,

adding water to the disintegrated diluted fraction to v increase thewater content until the diluted fraction is suspended in water ata'consistency below 1.5%, and a hydraulic centrifuging of this furtherdiluted fraction in a vortex pressure drop type centrifugal separator tofurther separate the fibrous and non-fibrous components into twoseparation products.

3. A method of separating bark, of the type having a fibrous component,into fibrous and non-fibrous components which comprises a wetdisintegration of the bark, adding water until the bark is suspended inwater at a consistency below 1.5%, a hydraulic centrifuging of the barkin a vortex pressure drop type centrifugal separator to substantiallyseparate the bark into a high proportion non-fibrous component and afibrous component, a wet screening of the fibrous component to yield twofractions, one fraction containing a high percentage of woody materialand the other fraction containing a high percentage of bark material, afurther hydraulic centrifuging of the fraction containing the highpercentage of bark material in a vortex pressure drop type centrifugalseparator to substantially separate said bark material into two furtherfractions, one of said further fractions containing a high percentage ofnon-fibrous bark material and the other of said further fractionscontaining a high percentage of fibrous bark material.

4. A method of separating bark, of the type having a fibrous component,into fibrous and non-fibrous components which comprises a wetdisintegration of the bark to substantially loosen the non-fibrouscomponent from the fibrous component and a hydraulic centrifuging tosubstantially separate the fibrous from the non-fibrous component, afurther wet disintegration of the non-fibrous component, adding wateruntil the disintegrated nonfibrous component is suspended in water at aconsistency below 1.5%, further hydraulically centrifuging in a vortexpressure drop type centrifuge separator the non-fibrous component tosubstantially separate the remaining fibrous material from thenon-fibrous material in the non-fibrous component.

5. A method of separating bark, of the type having a fibrous component,into fibrous and non-fibrous components which comprises a wetdisintegration of the bark to substantially loosen the non-fibrouscomponent from the fibrous component and a hydraulic centrifuging tosubstantially separate the fibrous from the non-fibrous component, a wetscreening of the fibrous component to substantially separate the coarsematerial from the less coarse material, recycling the coarse material tothe said wet disintegration, further hydraulically centrifuging in avortex pressure-drop type centrifuge separator the less coarse materialfor the separation of the fibrous and nonfibrous materials into twoproducts.

References Cited in the file of this patent UNITED STATES PATENTS 49,209Allen Aug. 8', 1865 222,171 Allen Dec. 2, 1879 1,057,151 Howard Mar. 25,1913 1,797,901 Darling Mar. 24, 1931 2,437,672 Anway Mar. 16, 19482,444,929 Hatch July 13, 1948 2,446,551 Pauley Aug. 10, 1948 2,530,181Schilling Nov. 14, 1950 2,627,375 Grondal et a1. Feb. 3, 1953 2,757,582Freeman et al Aug. 7, 1956 2,855,099 Koning Oct. 7, 1958 2,870,908 FitshJan. 27, 1959 2,877,953 Heritage et a1 Mar. 17, 1959 2,927,693 FreemanMar. 8, 1960 FOREIGN PATENTS 627,423 Great Britain Aug. 9, 1949 Y OTHERREFERENCES Chemical Engineering, March 1948, page 335, WeyerhaeuserSilvacon Advertisement.

Perry: Chemical Engineers Handbook, third edition, 1950, McGraw-HillBook Company, New York, page 931.

1. A METHOD OF SEPARATING BARK, OF THE TYPE HAVING A FIBROUS ANDGEL-LIKE COMPONENT INTO ITS PHYSICAL COMPONENTS WHICH COMPRISES A WETDISINTEGRATION OF THE BARK TO SUBSTANTIALLY LOOSEN THE SOLID NON-FIBROUSCOMPONENTS FROM THE FIBROUS AND COLLOIDAL GEL-LIKE COMPONENT, A HYDRALICCENTRIFUGING IN A VORTEX PRESSURE DROP TYPE CEN-